Flue pipe connection assembly and method of connection thereof

Abstract

A coupling between a stainless steel exhaust manifold of a recuperative heat exchanger and a plastic flue pipe. The internal integrity of the manifold is maintained by spot welding a mounting bracket to the outside thereby defining a slot between parallel portions of the bracket and the manifold. The flue pipe inserts through coaxial circular apertures in the bracket and the manifold. A shoulder of an annular protrusion on the outside of the flue pipe presses against an O-ring seated in an inwardly directed step of the circular aperture in the manifold thereby providing an airtight seal. The flue pipe is secured in the described position by a bifurcated retainer clip slid down into the slot thereby engaging portions of the opposite shoulder of the annular protrusion.

What is claimed is: 
     
       1. In combination: a recuperative heat exchanger for extracting heat from flue gases, said exchanger having a metallic exhaust manifold having a flat sheet wall with a circular aperture;   a bracket having an external connection to said flat sheet wall, said bracket defining a plate parallelly spaced from said wall of said manifold, said plate having a circular opening coaxial to said aperture, said opening being larger than said aperture;   a plastic pipe extending through said opening and into said manifold through said aperture, said pipe having an annular protrusion defining a first shoulder facing said manifold and a second shoulder facing away from said manifold;   an O-ring positioned around said pipe, said O-ring being pressed between said first shoulder and said wall of said manifold to form a substantially airtight seal therebetween; and   a bifurcated retainer removably inserted between said second shoulder and said plate, said retainer engaging said second shoulder to prevent motion of said pipe away from said manifold.   
     
     
       2. The combination in accordance with claim 1 wherein said heat exchanger comprises tubes surrounded by fins, the exhaust end of said tubes communicating with said exhaust manifold. 
     
     
       3. The combination in accordance with claim 1 wherein said external connection of said bracket to said wall defines spot welding. 
     
     
       4. The combination in accordance with claim 1 wherein said pipe is fabricated from PVC. 
     
     
       5. The combination in accordance with claim 1 wherein said aperture has an inwardly directed step, said O-ring being seated in said step. 
     
     
       6. An exhaust assembly for a recuperative furnace, comprising: a tube and fin recuperative heat exchanger for extracting heat from the products of combustion and for recovering latent heat of vaporization from said products of combustion by condensation within said tubes;   a metallic manifold coupled to the exhaust ends of said tubes of said recuperative heat exchanger, said manifold having a substantially flat sheet metal wall with an inwardly stepped circular aperture;   an elastic O-ring seated in the step of said stepped circular aperture;   a bracket having an external connection to said wall, said bracket defining a plate parallelly spaced from said wall of said manifold, said plate having an aperture coaxial with said aperture in said surface of said manifold;   a plastic pipe extending through said apertures in said plate and said manifold, said pipe having an annular protrusion defining a first shoulder facing said manifold and a second shoulder facing away from said manifold, said first shoulder being pressed against said O-ring wherein a substantially airtight seal is formed; and   a bifurcated retainer removably inserted between said plate and said second shoulder, said retainer engaging said second shoulder preventing said pipe from moving in a perpendicular direction away from said manifold.   
     
     
       7. The assembly recited in claim 6 wherein said pipe is PVC. 
     
     
       8. The assembly recited in claim 6 wherein said O-ring is compressed between said wall and said first shoulder. 
     
     
       9. The method of connecting a plastic flue pipe to a flat sheet metal wall of a manifold of a recuperative heat exchanger of a residential furnace, comprising the steps of: inserting said plastic flue pipe through a first circular aperture in a bracket plate externally connected to and parallelly spaced from said wall of said manifold and through a second circular aperture in said wall, said first and second apertures being coaxial, said pipe having an annular protrusion having a circumference larger than said second aperture but smaller than said first aperture, said protrusion defining a first shoulder facing said manifold and a second shoulder facing away from said manifold;   pressing said pipe inwardly towards said manifold to compress an elastic O-ring between said first shoulder and said wall of said manifold to form an airtight seal; and   inserting a bifurcated retainer between said plate and said surface of said manifold, said retainer engaging said second shoulder to prevent movement of said pipe in a direction perpendicular away from said manifold.